<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button>删除</button>
  <ul>
    <li>zsw</li>
    <li>lis</li>
    <li>wangwu</li>
  </ul>
  <script>
    var ul = document.querySelector('ul')
    var button = document.querySelector('button')

    button.onclick = function() {
      if(ul.children.length > 0) {
        ul.removeChild( ul.children[0] )  // 删除节点
      }
    }
    
  </script>
</body>
</html>